The present invention relates to a fixing apparatus by which a toner image formed by an electrophotographic method is fixed on the recording sheet, and particularly to a roller fixing apparatus and a belt fixing apparatus, by which the toner image is heated and fixed.
In a heat roller fixing apparatus, it is widely conducted that temperature of the fixing apparatus is controlled to a predetermined value by using a fixing temperature sensor such as a thermistor, or the like. In this case, it is normally conducted that a variation of the fixing temperature is reduced by using a plurality of heaters and by respectively on/off controlling them, and thereby fine fixing effects and stable fixing performance are secured.
In the on/off control of such the conventional fixing apparatus, there are following problems.
An image forming apparatus such as a copier, facsimile apparatus, into which the fixing apparatus according to the present invention is incorporated, is widely used in offices or shops, and is one of apparatus which are operated by the largest current. Almost all of the current supplied into the image forming apparatus is consumed in heaters of the fixing apparatus. Accordingly, power supply voltage is fluctuated when large current of heaters of the fixing apparatus is turned on/off, and the voltage supply onto the other apparatus in the room in which the image forming apparatus is installed, is affected. That is, such phenomena occur that illumination lamps in the room such as fluorescent lamps and incandescence lamps, flicker, thereby, environmental conditions of the room are badly affected.
In the present situation in which many OA apparatus are fully installed in the room and thereby, the environmental condition of the room is going to be worse, such the flicker of the room lamps is a problem to be solved. In the world, there is the trend to regulate such the flicker of the room lamps by regulations.
In the conventional technology in which the plurality of heaters are individually on/off controlled based on the fixing temperature sensors, there is a problem that the number of times of on/off operations is large, and thereby the number of occurrence of flickers is high.